There is a conventionally known inside plug, used for a container having a pouring spout from which content is poured, that seals the pouring spout with sealing means when not used and opens the pouring spout for the first time when used to ensure the virginity of a product. Food containers for dressing or sauce often adopt, as means for sealing the pouring spout of an inside plug, a so-called pull-ring type sealing member, which is molded integrally with the inside plug and opened by hooking a finger into the ring, pulling the ring, and tearing the thin border part with the inside plug body (PTL 1).
Although the conventional pull-ring type sealing member can be used for food containers having a relatively large size, the pull-ring type sealing member is not suitable for small containers such as cosmetic containers because, for example, the pull-ring cannot be accommodated in the space between the cap put on the neck part and the inside plug. Accordingly, another sealing member is proposed in which a small knob part that can be accommodated in the cap is provided in place of a pull-ring and the knob part is pulled to tear and open the sealing member (PTL 2). Since the pulling force applicable to a small knob part is smaller than that of a pull-ring, the part to be broken needs to be thinner so that the part can be opened with a small force. However, the conventional injection molding method has difficulty achieving both assurance of virginity and easy breakage in the thin part.
That is, when the thin part is too thin, an increase in the inner pressure of a container or an external pressing force may break the thin part, possibly losing virginity. In addition, when welds (junction marks generated in the confluence of molten resin) are generated in the thin part in the conventional injection molding, the thickness of the thin part may vary, possibly making it difficult to maintain sufficient airtightness and water-tightness.
However, when the thin part is thickened to ensure virginity and eliminate variations in injection molding due to welds, easy breakage is lost consequently and the thin part cannot be opened easily.
Accordingly, cosmetic containers or other containers perform sealing by pasting a hermetic seal (safety seal or virgin seal) as a separate member to the container pouring spout instead of adopting sealing means that tears and opens the sealing member (PTL 3).
However, such seal type sealing means has difficulty achieving both reliable sealing by a seal and easy removal. That is, when the adhesive strength (peeling strength) of a hermetic seal is increased to prevent the leakage of the content of a sealed container such as a skin toner, it is difficult to peel off the seal and results in inconvenience. Specifically, since cosmetic containers are used by women in many cases, if the peeling strength is increased, an attempt to peel off the hermetic seal may damage nails.
In addition, when the container pouring spout has a hermetic seal or the like which is made of a material different from that of the inside plug body, the hermetic seal and the inside plug body need to be formed as separate bodies and the process for adhering the inside plug to the hermetic seal is added, thereby causing a problem in that the cost becomes high and the number of manufacturing steps increases.
PTL 1: JP-A-2007-39060
PTL 2: JP-A-2002-166948
PTL 3: JP-A-2008-13226